Objective: The objective of this study is to identify the correlation between psychological factors and insomnia and the impact of insomnia on daytime sleepiness. Methods and Results: The participants were recruited through convenient sampling and consist of 173 working adults in Georgetown, Penang, aged 20 to 60 years. Participants completed the General Health Questionnaire (GHQ), Athens Insomnia Scale (AIS) and Epworth Sleepiness Scale (ESS). The results revealed that the prevalent of insomnia was 34.7%. There was a positive correlation between psychological distress and insomnia r = .481, p < .001 and also a positive correlation between insomnia and daytime sleepiness r = .334, p < .001. Conclusion: It is concluded that psychological distress typically causes sleep difficulties, and sleep deprivation leads to daytime sleepiness.